Field of the Invention
Certain embodiments disclosed herein relate generally to manway cover assemblies for railroad tank cars. The manway cover assemblies can also be used to control access to the interior of other types of tanks and structures.
Description of the Related Art
The current industry standard design for manway cover assemblies on railroad tank cars involves bolting down a cover with a series of eye bolts, many of the systems have a large number of bolts, such as 6 or 8 bolts. The design is very old and can result in costly failures for operators. Failures of the manway cover assemblies can result in daily fines accruing for the railroad operator.
The bolt-down design was originally intended to be secured by a hand wrench and tightened carefully in a star pattern. Crews charged with attaching the covers are under time pressures, thus, they commonly use impact wrenches while also ignoring the star pattern sequence. Common problems result from setting torque limits improperly and over tighten the nuts. This leads to stripped, stretched or broken eye-bolts, as well as deformed covers. Ultimately, the result is failure of the seal and leakage at the cover because of user error.